Process for producing ethylene/vinyl chloride copolymers



United States Patent 3,507,845 PROCESS FOR PRODUCING ETHYLENE/ VINYLCHLORIDE COPOLYMERS Edwin D. Hornbaker, Baton Rouge, La., assignor toEthyl Corporation, New York, N.Y., a corporation of Virginia No Drawing.Continuation of application Ser. No. 235,545, Nov. 5, 1962. Thisapplication Jan. 19, 1967, Ser. No. 610,452

Int. Cl. C08f J/60, 1/62, N74

US. Cl. 26087.5 Claims ABSTRACT OF THE DISCLOSURE A vinylchlorideethylene copolymer having a chemically combined ethylene contentof 922 percent by weight. The copolymer is characterized by having an1nherent viscosity at 25 C. of at least 0.9 when dissolved incyclohexanone at a concentration of 0.1 gram per 100 ml. The copolymeris prepared by copolymerizing vinyl chloride and ethylene at atemperature in the range of from about 25 C. to about 10 C. at apressure ranging from about 2,000 to about 30,000 p.s.i., in thepresence of a catalyst comprising the product of reaction between anorganoborane and at least one member of the group consisting ofmolecular oxygen and peroxides. Example of a suitable catalyst is theproduct of reaction between a trialkyl borane and molecular oxygen.

This is a continuation of application Ser. No. 235,545 filed Nov. 5,1962.

Novel vinyl chloride-ethylene copolymers and their production form theobjectives of this invention.

Polyvinyl chloride is a widely used commercial plastic material. Thepure polymer is relatively brittle and as a consequence it is normallycompounded with a plasticizer. Unfortunately, however, plasticizedpolyvinyl chloride possesses a number of shortcomings. For example, withall but the most expensive plasticizers the polymer becomes exceedinglybrittle when the temperature drops down to about 25 F. Furthermore, thecommonly used plasticizers tend to migrate from or bleed out of thepolymer or are often leached out when the polymer comes in contact withsuch common materials as soap and water, gasoline, other organicsolvents, and the like. On top of this, many of the commonly usedplasticizers tend to render the resultant plasticized polyvinyl chloridecomposition readily flammable and to impair its electrical resistivity.As a consequence, there is a distinct need in the art for a plasticmaterial which possesses the beneficial properties of plasticizedpolyvinyl chloride but which does not suffer from its shortcomings.

In accordance with this invention a new type of vinyl chloride-ethylenecopolymer is provided. This copolymer is characterized by containingfrom about 9 to about 22 weight percent of chemically combined ethylene,the balance being chemically combined vinyl chloride; and by having aninherent viscosity at 25 C. of at least about 0.9 (preferably from about0.9 to about 2.0) when dissolved in cyclohexanone at a concentration of0.1 gram per 100 ml. As is well known in the art, the inherent viscosityis a measure of the molecular weight of the polymer and therefore theforegoing inherent viscosities correspond in general to molecularweights ranging from about 75,000 to about 180,000.

The copolymers of this invention possess all of the beneficialproperties of plasticized polyvinyl chloride but are superior thereto ina number of important respects. In the first place, the presentcopolymers are self-extinguishing polymeric materials-eg, they do notsupport combustion even when exposed to an open flame. Secondly, thepresent polymers are less brittle at low temperatures 3,507,845 PatentedApr. 21, 1970 than conventional plasticized polyvinyl chloride. In fact,the novel copolymers of this invention have shown ASTM brittletemperatures as low as F. For purposes of comparison, plasticized vinylchloride specimens representative of those in commercial use have beenshown to have ASTM brittle temperatures of about 25 F.

Still another advantage of the present compositions is that it isunnecessary, though permissible, to utilize a plasticizer therewith.This in turn renders the present plastic compositions less expensive.

The present copolymers possess higher electrical resistivity and have alesser tendency to become brittle on aging than platicized polyvinylchloride. Also, the present copolymers are highly compatible with otherpolymers and resins, e.g., polystyrene, polyethylene, SBR,polyisobutylene, and the like. Consequently, the novel copolymersproduced in accordance with this invention are well suited for variousand sundry commercial uses.

A preferred embodiment of this invention relates to vinylchloride-ethylene copolymers as described above in which the content ofchemically combined ethylene ranges from about 9 to about 13 weightpercent. These particular copolymers possess the surprisingcharacteristic of being readily orientable-i.e., they can behot-stretched so as to further increase their strength. The proceduresfor effecting such hot-stretching are well known to the art and forfurther details reference may be had to Modern Plastics Encyclopedia, p.(1961). As an example of this unusual behavior, a copolymer of thisinvention composed of 12 weight percent of chemically combined ethyleneand 88 weight percent of chemically combined vinyl chloride and havingan inherent viscosity as measured above of 1.03 was found to have anultimate tensile strength (ASTM D-412) of about 46,000 p.s.i. afterbeing hot-stretched (200 F.) to a length six times its original length.

Another preferred embodiment of this invention involves vinylchloride-ethylene copolymers as defined above in which the content ofchemically combined ethylene is from about 15 to about 20 weightpercent, the balance being chemically combined vinyl chloride. Theseparticular polymers have ASTM brittle temperatures '(ASTM D-746) ofbelow about -50 F. Hence, these preferred copolymers are Well suited tolow temperature uses, uses to which even plasticized polyvinyl chlorideitself is unsuited.

A feature of this invention is the importance of having from about 9 toabout 22 weight percent of chemically combined ethylene in thecopolymer. A substantial amount of experimental work has shown that ifthe ethylene content is lower than this amount the resultant copolymerspossess virtually no flexibility even at room temperature. Rather, theselow content ethylene copolymers (e.g., 2 percent-see US. 3,051,689) arebrittle and tend to break very readily when subjected to a moderateflexing action.

Still another feature of this invention is the fact that a particularlyunique process is utilized in producing the present copolymers. Thisprocess involves copolymerizing ethylene and vinyl chloride at atemperature in the range of about 25 C. to about 10 C. using pressuresin the range of from about 2,000 to about 30,000 p.s.i. Thepolymerization catalyst used in this process is specific in itsapplicability and is the product of reaction between an organoborane andeither molecular oxygen (e.g., air) or a peroxide (e.g., cumenehydroperoxide) in proportions equivalent to an atomic ratio, elementalboron-to-elemental oxygen, of from about 0.25:1 to about 15: 1. The moleratio of the ethylene and the vinyl chloride used in this process is inthe range of from about 1:1 to about 4.5 :1.

To prepare the vinyl chloride-ethylene copolymers in which the contentof chemically combined ethylene ranges from about 9 to about 13 weightpercenti.e., the readily orientable polymers-the process described inthe preceding paragraph is used with the exceptions that the pressuresare kept in the range of from about 2,000 to about 15,000 p.s.i. and themole ratio of ethylene to vinyl chloride is kept in the range of fromabout 1:1 to about 2.5: 1. By the same token, the process described inthe preceding paragraph can be used to prepare the copolymers in whichthe content of chemically combined ethylene is from about 15 to about 20weight percenti.e., the copolymers having ASTM brittle temperatures ofbelow about 50 F by keeping the pressures in the range of from about4,000 to about 30,000 p.s.i. and by keeping the mole ratio of ethyleneto vinyl chloride in the range of about 2:1 to about 4.5: 1.

As noted above, the foregoing process embodiments are specific in theirapplicability to the synthesis of the novel copolymers of thisinvention. As a matter of fact, significant departures from any of theforegoing conditions will result at the very best in copolymers havingentirely different properties. Most of such departures result inpolymers having markedly inferior properties. The use of the molecularoxygen or peroxide in formulating the present catalyst system is ofconsiderable importance for still another reason. If this ingredient isomitted, the rate of polymerization is exceedingly slow. Consequently,by observing the combination of conditions specified above, the noveland highly useful copolymers of this invention are produced rapidly andin good yield.

A wide variety of organoboranes can be used in formulating the foregoingcatalyst systems. Triorganoboranes, such as trialkyl boranes,tricycloalkyl boranes, triaryl boranes, triaralkyl boranes, trialkarylboranes, and the like, are well suited although effective use can bemade of organoboron hydrides such as those having the formula RBH andwherein the R groups can be the same or different and are preferablyhydrocarbon groups such as alkyl, cycloalkyl, aryl, aralkyl, and alkarylradicals. Polymeric forms of borane such as diborane, tetraborane,pentaborane, hexaborane, and decaborane can also be used with success.The preferable organoboranes are the trialkyl boranes such as triethylborane, tri-n-propyl borane, triisopropyl borane, the tributyl boranes,the trihexyl boranes, the trioctyl boranes, and the like.

The preparation of the polymerization catalysts utilized in accordancewith this invention involves the formation of a reaction product betweenan organoborane, such as those described above, and either molecularoxygen or a peroxide compound, provided that the elementalboronto-elemental oxygen atom ratio therein is from about 0.25:1 toabout 15: 1. In preparing such reaction products apt concentrations ofthe organoborane and oxygen-containing material selected for use arebrought together preferably at low temperatures in the range of fromabout 78 C. up to about 50 C. To facilitate this reaction and simplifycatalyst handling, it is preferable to utilize an inert solvent such asan ether, an ester, a ketone, a hydrocarbon, or a like material which isliquid at the temperatures just described. Of the such solvents thecheapest and. most suitable are the aliphatic, cycloaliphatic, andaromatic hydrocarbons which remain in the liquid state of aggregation atthe selected temperature of from about -78 C. to about 50 C., examplesof these including cyclopentane, p cymene, 2 methylnonane, 2,3dimethylbutane, 2,2 dimethylbutane, 2 methylpentane, n hexane, 3methylpentane, 3 ethylpentane, 3,3 dimethylpentane, 2,4 dimethylpentane,2,2 dimethylpentane, nheptane, toluene, and the like. After bringing thereactive materials together, preferably in the solvent, the entiresystem is preferably agitated to insure intimate contact between thereactants. Depending upon the degree of agitation being utilized, thetime utilized to insure reaction of the organoborane with substantiallyall of the available 4 oxygen will range from about 5 minutes to about 6hours. In most instances, it is preferable to provide a residence timeor reaction period of from about 0.5 to about 1.5 hours. Thereupon, thecatalyst is charged into the polymerization vessel or zone and is in aform suitable for effecting the novel copolymerization reactions of thisinvention.

When utilizing air or oxygen as the oxygen-containing reactant, thecatalyst preparation procedure is simplified if the vessel in which thecatalyst is to be prepared is an autoclave or similar sealable devicefrom which all air can be evacuated after charging therein theorganoborane and, if used, the solvent. Thereupon, a metered amount ofair or oxygen gas can be readily introduced into the system so as toinsure the preparation of a catalyst containing the requisite ratio ofboron-to-oxygen.

In order to demonstrate the practice and advantages attendant thisinvention, an extensive series of experimental runs was conducted. Inthese experiments several procedures were utilized. One procedureidentified below as Procedure A was as follows:

A catalyst solution was prepared by adding to a cold solution(approximately 78 C.) of 2.5 grams of triethylborane in 10 ml. ofheptane in a closed stainless steel container a suflicient quantity ofair to provide 0.198 gram of oxygen. The solution was allowed to standat about 78 C. with periodic agitation for one hour before being used.(In a few cases, 30 ml. of heptane were employed and the procedure wasdesignated A-1.)

A cold l-liter autoclave was charged with the desired quantity of coldvinyl chloride (200 to 400 grams, depending upon the ethylene to vinylchloride desired), and while cooling in a Dry Ice-acetone mixture tomaintain the temperature at about 78 C. the autoclave was evacuated. Itwas then placed in a constant temperature bath and allowed to warm upsomewhat while agitating. The catalyst solution was then charged and theautoclave was pressurized with ethylene. During the pressurizingoperation, the autoclave came to the desired reaction temperature. Thequantity of ethylene charged was calculated from the volume of freespace in the autoclave before charging and from the density, this latterquantity being given by the temperature and pressure at the completionof charging. Agitation was continued for the desired reaction period, atthe end of which the autoclave was vented. The polymer formed waschopped in a Waring Blendor with methanol, filtered and dried at 50 C.

Procedure B involved the following steps:

A catalyst solution was prepared in the same manner as in Procedure Aexcept that after the 1-hour period the cold container was evacuated toremove any unreacted air. A cold high pressure autoclave containing thedesired quantity of vinyl chloride was cooled to about -78 C. in a DryIce-acetone mixture and the autoclave was evacuated. The autoclave wastransferred to a constant temperature jacket, the catalyst solution wascharged, agitation was started, and the reactor was pressurized withethylene. The autoclave warmed up sufficiently for appreciablepolymerization to start within 1 hour or less as indicated by a pressuredrop. Agitation was continued for the desired reaction period, at theend of which the autoclave was vented. The quantity of ethylene chargedwas calculated in the same way as in Procedure A. The polymer waschopped in a Waring Blendor with methanol, filtered and dried at 50 C.

Another techniqueProcedure Cwas as follows:

A cold 500 ml. high pressure autoclave containing the desired amount ofcold vinyl chloride maintained at about 78 C. in a Dry Ice-acetone bathwas evacuated, a solution of 1.25 grams triethylborane in 10 ml. ofheptane was charged and a quantity of air sufficient to provide 0.102gram of oxygen was added. The autoclave was transferred to a constanttemperature jacket, agitation was started and the autoclave waspressurized with ethylene. The autoclave had warmed up sufliciently forpolymerization to start within 1-1.5 hours. Agitation was continued forthe desired reaction period at the end of which the autoclave wasvented. The polymer was chopped in a Waring Blendor with methanolfiltered and dried at 50 C.

The results of these examples and the particular conditions used aremore fully described in Table I.

TABLE I.-COPOLYMERIZATION OF VINYL CHLORIDE AND ETHYLENE TO PRODUCEVINYL CHLORIDE-ETHYLENE COPOLYMERS OF THIS INVENTION Ethylene]Experivinyl Percent mental Reaction chloride Pressure, Conversion,ethylene Example procedure Temp., 0. time, hr. molar ratio p.s.i. x 10-percent in copolymer 11111h 1 A 4-8 4 2. 4 3. -3. 5 12 9. 7 1.15 A 17-16 2 2. 4 3.1-3.2 8 9. 9 1. 34 A 0-6 3 2. 4 2. 9-3. 0 7 10. 4 1. 10 A2-6 3 1. 9 2. 5-2. 9 9 10. 8 l. 38 A 17-15 3 1. 5 3. 1-3. 3 10 10. 4 1.70 A 4-6 4 1. 5 1. 8-3. 0 17 10. 6 1. 33 A-l 3-10 4 1. 4 1. 4-3. 0 3110. 1 0. 97 A 5-8 4 l. 5 1. 5-3.0 30 11. 1 1. 28 A 1-6 4 1. 9 1. 6-3. 025 12. 9 1. 10 A 2-6 4 2. 4 2. 0-3. 0 13. 4 0. 95 B -20-0 1. 5 2. 4 12.0-13. 0 17 16. 1 O. 90 11-1 1-5 4 4. 2 4. 5-5. 2 6 18. 9 1. 10 0 105 22. 7 13. 5-16. 5 20 20. 1 1. 23 C -10-2 2. 5 2. 8 11. 6-13. 8 19 20. 10. 94 B 20-0 2 2. 4 12. 0-14. 3 21 21. 4 0.98 B -10-6 2 3. 3 29-30 521.0 0. 95

1 Inherent viscosity at 0.

when dissolved in cyclohohexanone to a concentration of 0.1 gram per 100ml.

In Examples 12-14, inclusive, the concentration of thetriethylborane-oxygen catalyst was 0.14 mole percent based on totalmoles of ethylene plus vinyl chloride charged. In other examples theconcentration was 0.10 mole percent.

In Examples 1-16, inclusive, the boron-toelemental oxygen atomic ratiowas 2-1.

It will be seen from Table I that a wide variety of novel copolymers ofthis invention were produced in relatively short polymerization timesand in good conversions. Each of the copolymers so produced possessedthe characteristics of the polymers of this invention as discussedhereinabove.

To further demonstrate the excellent properties of the copolymers ofthis invention, the results of a number of standard evaluationprocedures are presented below. In general, these experiments involvedmeasuring important physical properties not only of various copolymersof this invention but of vinyl chloride-ethylene copolymers not of thisinventioni.e., copolymers which contain less than about 9 percent ofchemically combined ethylene. In addition, comparisons were made betweenthe physical properties of copolymers of this invention and commerciallyavailable plasticized polyvinyl chloride samples.

In one series of such tests, measurements were made of the ultimatetensile strength, ultimate elongation, brittle temperature, volumeresistivity, and flame resistance. The results of such tests are shownin Table II.

of plasticized polyvinyl chloride (i.e., plasticized PVC) had a watervapor permeability of 8.0 grams per 100 square inches per mil per 24hours.

As noted above, another embodiment of this invention relates to thesurprising discovery that the vinyl chlorideethylene copolymers of thisinvention in which the content of chemically combined ethylene rangesfrom about 9 to about 13 weight percent can be hot-stretched so as tofurther increase their strength. This process involves heating thecopolymer to a temperature of from about 100 to about 275 F. andpreferably from about 150 to about 240 F., and stretching the so heatedcopolymer to from about 1.5 to about 10 times its original length andpreferably from about 2 to about 8 times its original length. Thereupon,the copolymer is cooled while in the stretched condition and found topossess an increased tensile strength. Such hot-stretching can involveuniaxial hot-stretchingi.e., stretching of the copolymer sample in onedirection only. On the other hand, the hot-stretching can be effected ona biaxial basis whereby sequentially or preferably concurrently thesample is hot- TABLE II.IHYSICAL PROPERTIES OF COPOLYMERS OF THISINVENTION AS COMPARED WITH POLYMERS NOT OF THIS INVENTION TensileUltimate Volume strength, elongation, Brittle tempresistivity,Composition 1 p.s.i. percent erature, F. Flame resistance ohm-cm.

88-12 vinyl chloride-ethylene copolymer 000 105 57 N on-burning 10";80-20 vinyl chloride-ethylene copolymer 2,810 490 -120 do 96-4 vinylchloride-ethylene copolymer..- 4, 250 36 68 0.. 71-29 PVC,dioctylphthalate 3, 530 3 0 7 Burns 4.8 1013 67-33 PVC, dioctylphthalate2,600 3 5 do 1 Composition in weight percent. 2 ASTM D-412 3 ASTM D-7464 ASTM D-257 Another advantageous property possessed by the c0-stretched in two directions at right angles to each other.

polymers of this invention is their impermeability or exceedingly lowpermeability with respect to such materials as water, water vapor, andthe like. This valuable property renders the copolymers well suited foruse in packaging applications such as food wrappers and the like. As anexample of this behavior, a copolymer of this invention containing 90weight percent of chemically combined vinyl chloride and 10 weightpercent of chemically combined ethylene was subjected to a test todetermine the water vapor permeability thereof at 77 F.

In both cases, the strength of the hot-stretched copolymer of thisinvention is increased as compared with its original strength.

The novel copolymers and polymerization process of this invention shouldnot be confused with copolymers and copolymerization procedures referredto heretofore in the art. So far as is known and can be determined,vinyl chloride-ethylene copolymers having commercially attractiveproperties Were not prepared by previouslyknown procedures. It followstherefore that the copolymers of this invention and their novel methodof preparation are without precedent in the prior art. By way ofexample, an extensive series of experiments was conducted wherein priorart procedures for the preparation of vinyl chloride-ethylene copolymerswere repeated as closely as possible in order to determine thecharacteristics of these previously reported copolymers. The results ofthese experiments are summarized in Table III.

Certain other references to ethylene-vinyl chloride copolymers appear inthe prior art but were not repeated because in these instances thereported experimental work shows on its face that the resultantcopolymers were entirely different from the inferior to those of thepresent invention. For example, Belgian Patent 592,191, Examples 1 and2, describe the product as a viscous mass. Example 4 of that patentdescribes a yellow liquid and TABLE IIL-PROPERTIES OF PRIOR ART VINYLCHLORIDE-ETHYLENE COPOLYMER Patent Example N 0. (or Percent C HReference procedure) 1, inh in polymer Polymer properties 11.8.2,497,291 1 0. 53 32, 7 Weak, tacky, colorless.

2 0.43 26.0 Do. 2 0. 46 28. 3 Do. 3 No product obtained 4 0.29 7. 1Brittle, colorless. U-S- 2,422,392 1 0.40 47. 7 Weak, tacky, yellow.

2 0. 40 61.0 Weak, rubbery, brown 3 0. 50 2.3 Brittle, highly coloredmoldlngs. U.S. 2,388,225 5 0. 7O 44. 4 Weak, rubbery, orange,

6 0. 66 53. 3 Weak, possibly heterogeneous. U.S. 2,396,677 11 0. 53 40.3 Weak, tacky, tan. Belgian 592.191 3 0. 34 28.6 Weak, colorless.Australian 235,862 1 2 0.001 Trace yield of white powder.

2 No product obtained Australian 235 125 1 N product obtained I 2 Noproduct obtained British 767,417 14 0. 56 6. 2 White powder; brittlemolding.

14 0. 56 6. 2 D0. U.S. 2,985,633 14 l 0. 45 -100 White powder; weakmolding.

3 14 1 0.49 -10O White powder; brittle molding. 4 14 1 0. 46 -10() Do.14 l 0. 41 Do. Belgian 605,181 6 0. 81 3.0 Do. 6 0. 67 3. 0 Do. 7 6 0.659. 9 Do. Vysokomolek, Socdk.-- D 0. 8. 5 Do.

E 0. 13 45. 5 Tacky, viscous oil.

1 Determined in xylene at 100 C. Insoluble in cyclohexanone.

Z The trace of material isolated does not, in view of the low viscosity,appear to be polymeric.

3 Used 1.5 times the amount of vinyl chloride specified by Example 14. 4Used 3.75 t mes the amount of vinyl chloride specified by Example 14. 4Used 6.25 times the amount of vinyl chloride specified by Example 14.

6 Ran at 700 p.s.i. ethylene pressure instead of the 570 p.s.i.specified by the procedure of Example 6.

7 Ban at 950 p.s.i. ethylene pressure. 5 H. S. Kolesnikov et at.,Vysokornolek, Seed. 1, 627 (1959).

It will be seen from the above table that in conducting thecopolymerizations taught by Kolesnikov et al., procedures identified asD and B were utilized. The actual experimental procedures so used wereas follows:

PROCEDURE D An 845 ml. high pressure reactor cooled to about 78 C. wascharged with 170 grams of cold vinyl chloride and 165 grams of toluene.While continuing to maintain the temperature at about -78 C., thereactor was evacuated and a solution of 3.5 grams (2 weight percent onmonomer) of triisobutylborane in 9 grams of toluene was added from astainless steel cylinder. The reactor was pressurized with 500 p.s.i. ofethylene and allowed to warm with agitation during a 4.5 hour reactionperiod to 18 C., during which time the pressure was maintained at 500p.s.i. by intermittent addition of ethylene. The reactor was vented andthe toluene solution was concentrated and poured into methanol. Theproduct was filtered and dried. The yield was 9 grams.

PROCEDURE E Procedure D was repeated except that grams of vinyl chloridewere charged and the reactor was pressurized at about --78 C. to 800p.s.i. with ethylene. During the 4.5 hours required for the reactor towarm to 18 C., the pressure rose to 6,000 p.s.i. About 2 grams ofproduct were obtained by the workup method of Procedure D.

Reference to the information contained in Table III shows that all ofthe foregoing prior art procedures resulted in polymers which wereentirely different from and inferior to the novel copolymers of thisinvention. By way of example, the inherent viscosities of all of theseprior art copolymers were lower than those of the present invention,meaning that the prior art polymers had lower molecular weights. This inturn manifested itself in polymers having poor properties such as lowtensile strength, brittleness, or the like. None of these prior artcopolymers was suitable for use in applications to which the copolymersof this invention can be put.

Example 5 a viscous, sticky product. Similarly, Example 22 of US.2,471,959 reports a copolymer having an inherent viscosity of but 0.48which is characteristic of weak, tacky materials. The same holds true ofExample 8 of British Patent 578,584 which reports an inherent viscosityof only 0.38. Therefore, so far as is known and can be determined, thisinvention is the first instance whereby novel and highly usefulethylene-vinyl chloride copolymers having the properties discussed abovehave been found capable of preparation and have been prepared.

In conducting the polymerization reaction of this invention, severaltechniques can be advantageously used. Hence, the process can beconducted as a bulk polymerization procedure, as a suspension procedure,as an emulsion process or as a solution polymerization. The generaltechniques applicable to these various procedures are well known tothose skilled in the art and for further details reference may be had toSchildknecht, Polymer Processes, Interscience, New York, 1956, Chapters2, 3, 4 and 5. Generally speaking, it is preferable to conduct theprocess of this invention either in bulk or via a suspension techniqueutilizing an aqueous or aqueous alcohol suspension medium. Moreover, thepresent process can be conducted on a batch, semi-batch or continuousbasis, depending upon the mode of addition of the ingredients to thereaction zone.

Conventional polymer work up procedures are suitable for separating andrecovering the polymer from the reaction system. Exemplary of these workup procedures are those described in Schildknecht, Polymer Processes,Interscience, New York, 1956.

Examples of the organoboranes used in formulating the catalysts of thisinvention include triethyl borane, triisopropyl borane, tributyl borane,triisobutyl borane, tri-2- hexyl borane, tri-Z-methyl-l-butyl borane,tri-3-methyl- 3-pentyl borane, tricyclohexyl borane, tri-4-methylcyclohexyl borane, tri-beta-pinyl borane, tribenzyl borane, triphenylborane, tri-o-mor p-tolyl boranes, the various trixylyl boranes,tri-p-cumenyl borane, tri-Z-phenylethyl borane, di-Z-methyl-l-butylboron hydride, di-alpha-pinyl boron hydride, dicyclohexyl boron hydride,di-sec-hexyl boron hydride, di-alpha-naphthyl boron hydride,di-betanaphthyl boron hydride, dibenzyl boron hydride, di-3-methyl-Z-butyl boron hydride (i.e., bis-3-methyl-2-butyl borane),diethyl boron hydride (i.e., tetraethyl diborane), methyl borondihydride (i.e., dimethyl diborane), phenyl boron dihydride, benzylboron dihydride, and the like, including analogous compounds of thepolymeric boranes, such as pentaand decaborane. In general, suchorganoboranes will contain up to about 30 carbon atoms in each organicradical contained therein.

Exemplary of the peroxides which may be used in formulating the presentcatalysts are such compounds as the tert-alkyl hydroperoxides, thetert-aralkyl hydroperoxides, the di-tert-alkyl peroxides, and thediaroyl peroxides, all of which contain in general up to about 30 carbonatoms in the molecule. Specific examples of such compounds includetert-butyl hydroperoxide; tert-amyl hydroperoxide; 1,1-diethylpropylhydroperoxide; 1,1,2- trimethylpropyl hydroperoxide; 1,1,2,2tetramethylpropyl hydroperoxide; 1,1,3,3 tetramethyl-butylhydroperoxide; ,0: dimethylbenzyl hydroperoxide (i.e., cumenehydroperoxide); or methyl a ethylbenzyl hydroperoxide; ot,o!.diphenylethyl hydroperoxide; triphenylmethyl hydroperoxide;di-tert-butyl peroxide; tert-butyl-tert-amyl peroxide; di-tert-amylperoxide; di-(1,1,3,3-tetramethyl butyl) peroxide; dibenzoyl peroxide;di-p-toluoyl peroxide; bis-(m-chloro benzoyl) peroxide;bis-(p-chlorobenzoyl) peroxide; bis-(p-bromobenzoyl) peroxide; bis-(p-methoxybenzoyl) peroxide; bis-(p-cyanobenzoyl) peroxide;bis-(p-nitrobenzoyl) peroxide; ,B,,B'-(dinaphthoyl) peroxide; Decalinhydroperoxide (i.e., decahydronaphthalene hydroperoxide);bis-(l-hydroxycyclohexyl) peroxide; methane hydroperoxide;l-hydroxyheptaldehyde peroxide; methyl anyl ketone hydroperoxide;cyclohexanone peroxide; lauroyl peroxide, and the like. Another verysuitable peroxide compound is hydrogen peroxide.

Air or other suitable oxygen-containing gases may be used in conjunctionwith or in lieu of such peroxide compounds. Generally, the use of air ismost preferable.

The concentrations of catalysts utilized in the practice of thisinvention may be varied so long as the relative ratio of the elementalboron to elemental oxygen falls within the ranges discussed hereinabove.Generally speaking, the amount of organoboron ingredient charged to thepolymerization system will range from about 0.005 to about 0.5 molepercent based upon the total quantity of ethylene and vinyl chloridepresent in the system. Generally speaking, it is preferred to utilizeconcentrations ranging from about 0.02 to about 0.2 mole percent of theorgano-boron compound relative to the total moles of the monomers beingintroduced into the polymerization zone.

The polymerization timesi.e., the time during which the mixtures ofmonomers are allowed to remain in contact with the catalyst-do notappear to be particularly critical and thus may be varied to suit theneeds of the occasion. Generally speaking, polymerization times rangingfrom or 20 minutes up to about 6 to 18 hours may be used, depending uponthe polymerization temperature, the catalyst concentration, the amountof recycle used, if any, and the mode of operation. In general, it ispre ferred to use times ranging from about 1 to about 4 hours,especially when conducting the process of this invention in a continuousoperation.

The copolymers of this invention are suitable for use in the preparationof films, plastic sheets, funicular structures, bristles, fibers, wirecoatings, packaging materials, and the like. In general, the copoylmersof this invention are processed and handled in much the same manner asconventional plasticized polyvinyl chloride.

What is claimed is:

1. A process for producing vinyl chloride-ethylene copolymers comprising(A) from about 78 to about 91 weight percent vinyl chloride and (B) fromabout 9 to about 22 weight percent ethylene having an inherent viscosity at 25 C. of from about 0.9 to about 1.7 when dissolved incyclohexanone at a concentration of 0.1 gram per ml. an ASTM brittletemperature as low as F., and an ASTM tensile strength of up to about4000 p.s.i. which comprises copolymerizing ethylene and vinyl chlorideat a temperature in the range of from about 25 C. to about 10 C. at apressure in the range of from about 2,000 to about 30,000 p.s.i., in thepresence of a polymerization catalyst comprising the product of reactionbetween an organoborane and at least one member of the group consistingof molecular oxygen and peroxides; said organoborane catalyst beingselected from the group consisting of R B, R BH, and RBH wherein R is ahydrocarbon group containing up to about 30 carbon atoms and is selectedfrom the group consisting of alkyl, cycloalkyl, aryl, aralkyl, andalkaryl groups.

2. The process of claim 1 wherein the polymerization catalyst comprisesthe product of reaction between an organoborane and at least one memberof the group consisting of molecular oxygen and peroxides in proportionsequivalent to an atomic ratio, elemental boron-to-elemental oxygen, offrom 0.25:1 to about 15:1.

3. The process of claim 1 wherein the mole ratio of ethylene to vinylchloride is from about 1:1 to about 4.5:1.

4. The process of claim 1 wherein the copolymerization is conducted at atemperature of from about 0 C. to 6 C. and at a pressure of from about2,900 to about 3,000 p.s.i., in the presence of a polymerizationcatalyst comprising trialkylborane and molecular oxygen in proportionsequivalent to an atomic ratio, elemental boron-toelemental oxygen of2:1; the mole ratio of the ethylene to vinyl chloride being 2.4: 1.

5. The process of claim 4 wherein the trialkylborane is triethylborane.

6. The process of claim 1 wherein the polymerization catalyst utilizedis the product of reaction between a trialkylborane and lauroylperoxide.

7. The process of claim 1 wherein the polymerization catalyst utilizedis the product of reaction between a trialkylborane and molecularoxygen.

8. The process of claim 1 wherein the polymerization is conducted at atemperature in the range of -20 C. and 0 C. and the pressure is in therange of 12,000 to about 13,000 p.s.i.

9. The process of claim 1 wherein the polymerization is conducted at atemperature in the range of from about 20 C. to about 10 C. and at apressure of from 4,000 to about 15,000 p.s.i.

10. The process of claim 9 wherein the polymerization is conducted at apressure in the range of from about 12,000 to about 14,300 p.s.i.

Flory: Principles of Polymer Chemistry, Cornell University Press,Ithaca, N.Y. (1953), CD281, P6F66 (pp. 133 and relied on).

Stille: Introduction to Polymer Chemistry, John Wiley and Sons, Inc.,New York (1962), QD281, PS7 (p. 25 relied on).

JOSEPH L. SCHOFER, Primary Examiner JOHN A. DONAHUE, JR., AssistantExaminer

